The invention relates to a stator wheel for a turbine engine, in particular an aviation gas turbine engine on an industrial turbine, where such a stator wheel forms a turbine nozzle or a compressor diffuser.
Improving the performance of turbine engines and reducing their polluting emissions leads to ever-higher operating temperatures being envisaged.
For the elements in the hot portions of turbine engines, proposals have thus been made to use ceramic matrix composite (CMC) materials. Such materials present remarkable thermostructural properties, i.e. mechanical properties that make them suitable for constituting structural elements combined with the ability to conserve these mechanical properties at high temperatures.
Furthermore, CMC materials are of much lower density than the metal materials conventionally used for making the elements in the hot portions of turbine engines.
Thus, documents WO 2010/061140, WO 2010/116066, and WO 2011/080443 describe making turbine engine blades with integral inner and outer platforms. The use of CMC material specifically for turbine nozzles has also been proposed, in particular in document WO 2010/146288.
Traditional metal turbine nozzles are usually built by assembling together a limited number of sectors obtained by casting, each sector having quite a large number of vanes. The complex shape of such sectors makes them difficult to obtain as a single piece of CMC material. In order to obtain a turbine nozzle made of CMC material, it has therefore been necessary to envisage assembling together a relatively large number of individual elements, or vanes, each vane having only a small number of airfoils, and possibly only one airfoil. This leads to a problem of making an assembly of nozzle vanes simply and economically while achieving satisfactory sealing, in particular for the purpose of avoiding leaks between the gas flow passage through the turbine and the outside of the nozzle.
A similar problem arises with making turbine engine compressor diffusers, either using CMC materials in the downstream compressor stages that are exposed to higher temperatures, or else using organic matrix composite (OMC) materials, at least in the upstream compressor stages.